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bridrive55 · Jul 13th, 2006, 03:15 PM

Hey guys,
Considerable evidence points to the conclusion that the stock KA24DE OBDI (and KA24E) oxygens sensor band is exceeded by the fuel/air ratios generated when a turbocharger generates atmospheric pressure (manifold neutral pressure, reads 0psi on a vacuum gauge). This preboost spool occurs during regular driving every time the throttle plate is not fully open and manifold (post throttle body) pressure is between 4"Hg and 3-4psi boost. The factory ECU map cannot compensate for the increased air, and unilinear A/F curve adjustments will not compensate for this! Preboost leanout will hurt your KA, so I strongly advise all turbocharged KA's to take extra care in enriching the fuel/air mixture in that pressure range. I recommend usining wideband oxygen sensing and an earlier fuel pressure onset if possible.

The OBD-II oxygen sensors have a wider band (wider voltage range), and this might compensate for preboost leanout. Once again, this is only a consideration on turbocharged vehicles.

Jul 13th, 2006, 03:15 PM	#26 (permalink)
bridrive55 KA24DET Join Date: Aug 2004 Location: UW Madison Posts: 1,000	DANGER: KA leanout! Hey guys, Considerable evidence points to the conclusion that the stock KA24DE OBDI (and KA24E) oxygens sensor band is exceeded by the fuel/air ratios generated when a turbocharger generates atmospheric pressure (manifold neutral pressure, reads 0psi on a vacuum gauge). This preboost spool occurs during regular driving every time the throttle plate is not fully open and manifold (post throttle body) pressure is between 4"Hg and 3-4psi boost. The factory ECU map cannot compensate for the increased air, and unilinear A/F curve adjustments will not compensate for this! Preboost leanout will hurt your KA, so I strongly advise all turbocharged KA's to take extra care in enriching the fuel/air mixture in that pressure range. I recommend usining wideband oxygen sensing and an earlier fuel pressure onset if possible. The OBD-II oxygen sensors have a wider band (wider voltage range), and this might compensate for preboost leanout. Once again, this is only a consideration on turbocharged vehicles. __________________ StreetTech S13 KA24DET, .70A/R T04E, FMIC, VLSD, SAFC-II, 550cc's, Q45 MAF.